Above is a block diagram of MSSLís CCD Test Facility, which is situated
in MSSLís class 100 cleanroom. The CCD and its FPA card are mounted
on an X-Y stepper motor system in a vacuum chamber and the CCD is cooled
using a flexible attachment to a LN2 reservoir which is built into the
chamber. A window in the chamber wall permits the CCD to be illuminated
from outside the chamber. This allows various optical setups to be used
and changed (e.g. pinpoint illumination, flat-field, focussed image) without
disturbing the CCD. The window and optical bench are in a dark enclosure
to eliminate external light. The X-Y stepper system allows the CCD to be
moved in the optical beam to expose different areas of the CCD to the same
optical flux, e.g. to perform flat-fielding, and also allows a calibrated
photodiode to be placed in the beam for flux measurement.

Heaters on the support plate for the CCD allow the temperature to be
controlled. A 4-wire rhodium-iron thermometer is used to measure the temperature.

The experiment control and data acquisition PC communicates with the
stepper motor controller via an RS-232 serial link.

The ROE generates the clock pulse sequences to shift and readout the
CCD. It also performs CDS on the video signals from the FPA card, digitises
the video and buffers the digital data. The ROE is highly flexible, allowing
the PC to control integration, windowing, binning , readout direction,
etc...

The PC contains a custom-built ISA card to interface with the
ROE. This card has several functions:-

Control of ROE using bilevel lines and a 64Kbaud RS232 link.

Control of clocking rate

Readback of digitised data over a pair of 5MBaud RS-422 synchronous
links (one for left port and one for right).

Operation of shutter to control exposure.

A PCI card in the PC handles DMA transfer of the data into PC memory.

The bias/jitter-clocking box allows the PC to control CCD bias voltages
and jitter/dither-clocking.

The whole setup is controlled from the PC using the IDL programming
language. This allows interactive or program control and seamless inclusion
of graphics for near-realtime display. The high-level software is written
in IDL, while some low-level routines are written in C and called as DLLs.
Another benefit of IDL is that the same analysis programs can be run locally
on the PC or on the MSSL network (SUNs and DEC Alphas).